Recording Media Having a Nanocomposite Protection Layer and Method of Making Same

ABSTRACT

A method includes: forming a recording layer on a substrate and depositing a nanocomposite layer on the recording layer, the nanocomposite layer including a wear-resistant material and a solid lubricant material, wherein the atomic percentage of the solid lubricant material in the nanocomposite layer is in a range from about 5% to about 99%.

CROSS-REFERENCE TO A RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 12/348,443, filed on Jan. 5, 2009, which is hereby incorporatedby reference.

BACKGROUND

An overcoat layer is commonly placed on top of magnetic recording mediato protect the magnetic media layers under the overcoat from corrosion.The overcoat can serve to reduce friction and wear caused byintermittent head-disc contact. One well-known overcoat material isdiamond-like carbon (“DLC”) material. A typical thickness of the DLCovercoat layer ranges from 2.5 nm to 4.0 nm.

On top of this overcoat layer, there is usually a thin layer of liquidlubricant that acts as the buffer layer to further reduce corrosion, aswell as to serve as a lubricating layer for the air bearing slider toglide over. A typical lubricant is a perfluoropolyether (PFPE), e.g.,Fomblin® Z and Y lubricants from Solvey Solexis Inc. A typical thicknessof the lubricant layer is between 1 nm and 2 nm.

As the areal density is increased in hard disk drive industry, thehead-to-media spacing (HMS) must also be reduced. To this end, it isdesirable to provide an alternative to the current two protectionlayers, e.g., lubricant and overcoat.

SUMMARY

A method includes: forming a recording layer on a substrate anddepositing a nanocomposite layer on the recording layer, thenanocomposite layer including a wear-resistant material and a solidlubricant material, wherein the atomic percentage of the solid lubricantmaterial in the nanocomposite layer is in a range from about 5% to about99%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a prior art storage media.

FIG. 2 is a schematic representation of a storage media in accordancewith an aspect of the invention.

FIG. 3 is a schematic representation of a storage media in accordancewith another aspect of the invention.

FIG. 4 is a schematic representation of a storage media in accordancewith another aspect of the invention.

FIG. 5 is a schematic representation of a storage media in accordancewith another aspect of the invention.

FIG. 6 is a graph of surface energies of multilayer PTFE/carbon samples.

FIG. 7 is a graph of corrosion results of two samples.

DETAILED DESCRIPTION OF THE INVENTION

This description provides a recording media having a nanocompositeprotection layer that can be used in magnetic recording applications.

FIG. 1 is a schematic representation of a prior art storage media 10that can be used. The storage media 10 includes a recording layer 12 ona substrate 14. An overcoat 16 is positioned on the recording layer. Aliquid lubricant 18 is positioned on the overcoat 16.

FIG. 2 is a schematic representation of a storage media 20. The storagemedia 20 of FIG. 2 includes a recording layer 22 on a substrate 24, anda single protection layer 26 on the recording layer 22. As used herein,a recording layer 22 comprises one or more layers of material that areused to store information. The recording layer 22 may include a stack ofone or more magnetic layers, underlayers, interlayers, or other layers.Thus, a recording layer may encompass multiple layers in the variousembodiments.

The single protection layer 26 comprises a nanocomposite layer includinga wear-resistant material and a solid lubricant material. In thefollowing description the wear-resistant material is referred to as ahard material and the solid lubricant material is referred to as a softmaterial.

The soft material provides low friction and low surface tension, whilethe hard material provides high hardness and density. The totalthickness of the protection layer is between about 0.5 nm and about 5nm, and the hard material has a hardness of 10 GPa or above.

The structure illustrated in FIG. 2 provides improved thermal stabilitycompared to the structure of FIG. 1 due to the removal of liquidlubricant layer, which in one embodiment, enables it to be applied inheat-assisted magnetic recording (HAMR). In addition, the compositeprotection layer provides improved corrosion protection, not only byinclusion of a high-density hard material, but also by having alow-surface tension (i.e., high water resistance). Furthermore, thesingle protection layer 26 of FIG. 2 can have a lower overall thicknessdue to the one-layer composite design.

The soft material in the protection layer 26 should have low surfacetension, good lubricity, and optionally, high thermal stability.Examples of such materials include sputtered polytetrafluoroethylene(“PTFE”), CVD PTFE, and CF_(x) film prepared by plasma enhanced chemicalvapor deposition (“PECVD”). Another example is sputtered WO_(x). Thehard material should have high density and high hardness. Examples ofsuch materials include diamond-like carbon (“DLC”) deposited by sputteror ion beam deposition (“IBD”) or filtered cathodic arc (“FCA”) methods.Other examples include, but are not limited to, Al₂O₃, SiN, TiN, TiC,and YSZ.

The single protection layer 26 can be prepared by several methods. Inone method, the hard and soft materials are co-deposited, e.g.,co-sputtered, using two separate sputter targets. The mole ratio betweenthe soft material and the hard material in the protection layer canrange from about 0.2 to 100.

Another method uses a composite target during the deposition, e.g.,sputter. Either RF or DC sputter can be utilized depending on thematerial choices. The mole ratio between the soft material and the hardmaterial could range from about 0.2 to 100.

In a CVD case, two or more precursor gases can be used to achieve thedesired structure. Examples of such precursor gases include: C₂H₂ andCF₄ or CHF₃ or C₂F₄.

Another method uses a layer-by-layer deposition, e.g., alternatelysputtering a soft material and a hard material. The thickness of eachlayer could be in a range from about 0.2 nm to about 2 nm. The ratiobetween soft material and hard material could range from about 0.2 to100. The total number of “layers” could be between 2 and 25.

The performance of the protection layer can be tailored by adjusting theratio between the soft and hard materials to achieve performance similarto that of the previously used liquid lubricant or overcoat. In someapplications, a liquid lubricant can also be added to the protectionlayer to achieve the desired properties.

FIG. 3 is a schematic representation of a storage media 30 in accordancewith another aspect of the invention. The storage media 30 of FIG. 3includes a recording layer 32 on a substrate 34, a single protectionlayer 36 on the recording layer 32, and a liquid lubricant layer 38 onthe protection layer 36. In this case, the protection layer 36 replacesthe overcoat layer 16 of FIG. 1, and may provide better corrosionprotection due to the combination of the low surface energy (high waterresistance) of the soft material and the high density of the hardmaterial.

In other applications, the protection layer can be coated on theovercoat, e.g., Ion Beam Deposition (IBD) carbon, to achieve the desiredproperties. FIG. 4 is a schematic representation of a storage media 40in accordance with another aspect of the invention. The storage media 40of FIG. 4 includes a recording layer 42 on a substrate 44, an overcoatlayer 46 on the recording layer 42, and a single nanocompositeprotection layer 48 on the overcoat layer 46. In this case, theprotection layer 48 serves as the lubricant.

Specific examples of the application of a protection layer to a storagemedia are set forth below. In the examples, the Co layer serves as atesting layer. It should be noted that the Co layer in the example canbe replaced by a recording layer, as defined above.

EXAMPLE 1

A glass substrate was sputtered with Cobalt via a conventional DCsputter to form a 10 nm thick Co layer on the substrate. Then, thesample was co-sputtered with PTFE and YSZ to form a protection layer onthe Co layer. Co-sputter can be implemented by utilizing two separate RFsputter targets in a conventional sputter system that allows RFco-sputter of two targets. The sputter rates are adjusted so that thetotal thickness of the protection layer can range from about 2 nm toabout 5 nm. The PTFE atomic percentage in the resulting film can varyfrom about 5% to about 99%, depending on the application.

EXAMPLE 2

A glass substrate was sputtered with Cobalt via a conventional DCsputter to form a 10 nm thick Co layer on the substrate. Then, thesample was co-sputtered with PTFE and Al₂O₃ to form a proctection layeron the Co layer. Co-sputter can be implemented with a conventionalsputter system with co-sputter function. The sputter rates can beadjusted so that the total thickness of the film can range from about 2nm to about 5 nm The PTFE atomic percentage in the resulting film canvary from about 5% to about 99%, depending on the application. The fullstructure magnetic media can be manufactured with the same sputtersystem with the procedure, as mentioned above.

EXAMPLE 3

A glass substrate was sputtered with Cobalt via a conventional DCsputter to form a 10 nm thick Co layer on the substrate. Then, thesample was sputtered with a composite target made of PTFE and graphiteto form a protection layer on the Co layer. The fabrication process ofthe composite target is as follows. Machine the PTFE/graphite compositesheet to the desired geometry. Then, etch the one side of the sheet withsodium solution. Afterwards, the sheet is bonded to a copper backingplate with a conductive epoxy. The sputter rate is adjusted so that thetotal thickness of the film can range from about 2 nm to about 5 nm. ThePTFE atomic percentage in the target can vary from about 5% to about99%, depending on the application.

EXAMPLE 4

A glass substrate was sputtered with Tantalum to form a 10 nm thicknessof Tantalum on the substrate. Then, the sample was sputtered vialayer-by-layer deposition of PTFE and carbon alternatively. For bothPTFE and carbon, the sputter rate was calibrated by an X-rayReflectometry (XRR) measurement of a thick film. The sputter time ofeach target is adjusted so that the desired structure is achieved. FIG.5 is a schematic representation of a storage media 50 in accordance withan aspect of the invention. The storage media 50 of FIG. 5 includes arecording layer 52 on a substrate 54, and a multilayer protection layer56 on the recording layer 52. The protection layer 56 includesalternating layers of PTFE and carbon.

FIG. 6 is a graph of surface energies of multilayer PTFE/carbon samples,wherein line C1 is for a Glass/Ta magnetic media; C2 is for aGlass/Ta/carbon 4 nm; C3 is for a Glass/Ta/PTFE 4 nm; C4 is for aGlass/Ta/carbon 2 nm/PTFE 2 nm; C5 is for a Glass/Ta/(carbon 1 nm/PTFE 1nm)₂; and C6 is for a Glass/Ta/(carbon 0.5 nm/PTFE 0.5 nm)₄. As can beseen from the data in FIG. 6, even when the top PTFE layer is as thin as0.5 nm, the surface energy is low. This is especially true for the polarsurface energy, which suggests that the protection layer has high waterresistance.

EXAMPLE 5

A glass substrate was sputtered with cobalt via a conventional DCsputter to form a 10 nm thick Co layer on the substrate. Then, thesample was sputtered with 3 nm carbon followed by 1.5 nm PTFE. The PTFEsputter condition is as follows. The RF power is 200 W, and the Ar flowrate is 112 sccm. The carbon sputter condition is as follows. The DCpower is 737 W, the Ar flow rate is 39 seem, and the H₂ flow rate is 19seem. For both PTFE and carbon, the sputter rate was calibrated by XRRmeasurement of a thick film. The sputter time of each target is adjustedso that the desired film thickness is achieved. As a reference forGlass/Co/carbon 3 nm/PTFE 1.5 nm sample, a Glass/Co/carbon 5 nm samplewas also made. FIG. 7 is a graph of corrosion results of the twosamples. As shown in FIG. 7, the combination of low surface energy andhigh density is more effective in corrosion protection than high densityalone.

While the invention has been described in terms of several examples, itwill be apparent to those skilled in the art that various changes can bemade to the disclosed examples without departing from the scope of theinvention, as defined by the following claims. The implementationsdescribed above and other implementations are within the scope of theclaims.

1. A method comprising: forming a recording layer on a substrate; anddepositing a nanocomposite layer on the recording layer, thenanocomposite layer including a wear-resistant material and a solidlubricant material, wherein the atomic percentage of the solid lubricantmaterial in the nanocomposite layer is in a range from about 5% to about99%.
 2. The method of claim 1, wherein the wear-resistant material has ahardness of at least 10 GPa.
 3. The method of claim 1, wherein thewear-resistant material comprises at least one of: diamond-like carbon,Al₂O₃, SiN, TiN, TiC or YSZ.
 4. The method of claim 1, wherein the solidlubricant material comprises at least one of: sputtered PTFE, orchemical vapor deposited CF_(x), or WO_(N).
 5. The method of claim 1,wherein: the nanocomposite layer has a thickness in the range from about1 nm to about 5 nm.
 6. The method of claim 1, wherein the step ofdepositing a nanocomposite layer on the recording layer comprises:co-deposition of the wear-resistant material and the solid lubricantmaterial.
 7. The method of claim 1, wherein the step of depositing ananocomposite layer on the recording layer comprises: co-sputtering thewear-resistant material and the solid lubricant material using twoseparate targets.
 8. The method of claim 1, wherein the step ofdepositing a nanocomposite layer on the recording layer comprises:sputtering the wear-resistant material and the solid lubricant materialusing a composite target.
 9. The method of claim 1, wherein the step ofdepositing a nanocomposite layer on the recording layer comprises:depositing the wear-resistant material and the solid lubricant materialin alternating layers.
 10. The method of claim 9, wherein the number oflayers is in a range of from 2 to about
 25. 11. The method of claim 9,wherein the thickness of the layers is in a range from about 0.2 nm toabout 2 nm.
 12. The method of claim 1, further comprising: depositing anovercoat layer between the nanocomposite layer and the recording layer.13. The method of claim 12, wherein the overcoat layer comprises: ionbeam deposited carbon.
 14. The method of claim 1, wherein the thicknessof the protection layer is in a range of from about 0.5 nm and about 5nm.
 15. A method comprising: forming a recording layer on a substrate;and depositing a nanocomposite layer on the recording layer, thenanocomposite layer including a wear-resistant material and a solidlubricant material, wherein the mole ratio between the solid lubricantmaterial and the wear-resistant material is in a range from about 0.2 toabout
 100. 16. The method of claim 15, wherein the step of depositing ananocomposite layer on the recording layer comprises: co-deposition ofthe wear-resistant material and the solid lubricant material.
 17. Themethod of claim 15, wherein the step of depositing a nanocomposite layeron the recording layer comprises: co-sputtering the wear-resistantmaterial and the solid lubricant material using two separate targets.18. The method of claim 15, wherein the step of depositing ananocomposite layer on the recording layer comprises: sputtering thewear-resistant material and the solid lubricant material using acomposite target.
 19. The method of claim 15, wherein the step ofdepositing a nanocomposite layer on the recording layer comprises:depositing the wear-resistant material and the solid lubricant materialin alternating layers.
 20. The method of claim 19, wherein the number oflayers is in a range of from 2 to about 25.